Smart cards have become widespread as the uses for such cards multiplies. Subway riders can now purchase a card with a desired value programmed into the card, with the stored value decreasing by an amount equal to the fare each time the user uses the card to gain access to the subway system. Similar cards are used in vending machines, allowing users to carry one card to use for all their vending purchases instead of needing change or single dollars. The programmed amount on the card is reduced each time a purchase is made. Prepaid telephone smart cards are also popular.
Furthermore, smart cards that do not store cash information can also be used. For example, drivers licenses can store personal or medical data, etc.
One disadvantage with smart cards is that the user has no easy way of determining the data that is stored on the card unless he or she remembers it. If the user forgets, then he or she must normally go to a machine that accepts such cards to find out what is stored on the card (e.g., the amount of money that is left on the card.)
Portable card readers have been developed to allow a user to more easily determine the remaining value on all the cards in his or her possession. Such a reader, for example, is shown in U.S. Pat. No. 5,015,830 to Masuzawa et al. and features a reader having a slot into which the card is inserted, electronic reading circuits for reading the information stored on the card and a display for displaying the read information to the user. Although the Masuzawa device is small enough to be portable, it is, nevertheless, too large for many users to carry it around with them on a regular basis. Furthermore, the slot on such a device traps dirt and debris which can eventually render the device inoperative.